Reference signal sending method, reference signal receiving method, network device, and terminal device

ABSTRACT

A reference signal sending or receiving method includes: determining, by the network device, a plurality of resource elements REs used to carry a first CSI-RS, where the plurality of REs are distributed in a plurality of resource units, and in each resource unit, a plurality of REs used to carry the first CSI-RS are located on a plurality of subcarriers in a same symbol, values of the first CSI-RS carried on at least two REs are different, and values of the first CSI-RS are loaded to the plurality of REs in the resource unit by using a first multiplex code; and sending, by the network device, the first CSI-RS to the terminal device by using the plurality of REs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2018/084044, filed on Apr. 23, 2018, which claims priority toChinese Patent Application No. 201710295299.1, filed on Apr. 28, 2017.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and morespecifically, to a reference signal sending method, a reference signalreceiving method, a network device, and a terminal device.

BACKGROUND

In a new radio access technology (NR) system, to support high-frequencywireless communication, impact caused by phase noise and switching ofanalog beams needs to be considered for resource configuration of achannel state information-reference signal (CSI-RS). A high-frequencywireless communication system uses spectrum resources in a highfrequency band, to implement high-rate short-distance transmission andmeet requirements on a 5G capacity and transmission rate. However, inthe high-frequency wireless communications system, the phase noise ismuch less sensitive to frequency than to time, and to overcome a highpath loss in the high frequency band, a physical layer needs to use ahigh-gain narrow beam antenna to improve coverage of a communicationslink. In such a process, the antenna may need to frequently switchbetween beams. The various factors described above require that acommunications device complete channel measurement within a short periodof time, to reduce the impact caused by the phase noise and impactcaused to beam switching. Therefore, in the NR, it is considered toconfigure CSI-RSs in a same symbol (for example, an orthogonal frequencydivision multiplexing (OFDM) symbol).

On the other hand, as multi-antenna technologies develop, CSI-RSs atdifferent antenna ports in a same network device may be multiplexed on aresource through code division, in other words, code divisionmultiplexing (CDM). For example, the network device distinguishesbetween the different antenna ports by using different orthogonal covercodes (OCC). In the NR, to ensure that CSI-RSs at each antenna port areconfigured in a same symbol, resources of different antenna ports may bedistinguished through frequency domain CDM, for example, frequencydomain CDM2 and frequency domain CDM4. However, when a plurality ofnetwork devices send CSI-RSs by using a same antenna port and a sametime-frequency resource, a same OCC code may be used. In this case,although the two CSI-RSs use different identifiers N_(ID) ^(CSI), thetwo CSI-RSs may still be strongly correlated and cause interference toeach other.

SUMMARY

This application provides a reference signal sending method, a referencesignal receiving method, a network device, and a terminal device, toreduce correlation between CSI-RSs and reduce interference causedbetween the CSI-RSs.

According to a first aspect, a reference signal sending method isprovided. The method includes: determining, by a network device, aplurality of resource elements (REs) used to carry a first CSI-RS, wherethe plurality of REs are distributed in a plurality of resource units,where in each resource unit, a plurality of REs used to carry the firstCSI-RS are located on a plurality of subcarriers in a same symbol,values of the first CSI-RS carried on at least two REs are different,and values of the first CSI-RS are loaded to the plurality of REs in theresource unit by using a first multiplex code; and sending, by thenetwork device, the first CSI-RS to a terminal device by using theplurality of REs.

It should be noted that the first CSI-RS may be selected from a firstpilot sequence generated by the network device in advance. In otherwords, the first CSI-RS includes some or all sequence elements in thefirst pilot sequence. In this embodiment of the present invention, eachsequence element in a pilot sequence may be referred to as a value of aCSI-RS, and a quantity of sequence elements in the pilot sequence may bereferred to as a sequence length of the pilot sequence. Correspondingly,a quantity of different CSI-RS values of a CSI-RS at each antenna portin each symbol in each resource unit is referred to as a sequence lengthof the CSI-RS at the antenna port in the symbol in the resource unit. Itmay be understood that each CSI-RS value corresponds to a sequenceelement in the pilot sequence, and different CSI-RS values correspond todifferent sequence elements in the pilot sequence. In the prior art, aplurality of REs in a same symbol in a same resource unit carry a sameCSI-RS value. In other words, a CSI-RS at each antenna port has a symbollength of 1 in one symbol in one resource unit. However, in thisembodiment of the present invention, a CSI-RS at each antenna port has asequence length of at least 2 in each symbol in each resource unit.Compared with the prior art, the sequence length is increased andcorrelation between sequences is reduced. Therefore, when two networkdevices send CSI-RSs by using a same time-frequency resource and a samemultiplex code, because the CSI-RS provided in this embodiment of thepresent invention is used, a sequence length in a same symbol in eachresource unit is increased, and correlation between sequences isreduced, so that interference between the two CSI-RSs is reduced,thereby facilitating channel estimation and improving quality of areceived signal.

Optionally, before the determining, by a network device, a plurality ofREs used to carry a first CSI-RS, the method further includes:generating, by the network device, the first pilot sequence, where thevalues of the first CSI-RS are selected from the first pilot sequence.

In other words, the first CSI-RS is generated by using some or allsequence elements in the first pilot sequence. The first pilot sequencemay be generated according to a pilot sequence generation method in theprior art, or may be generated according to the method in thisembodiment of the present invention.

In other words, the network device generates the first pilot sequencebased on a first parameter, and then maps the some or all sequenceelements in the first pilot sequence onto the plurality of REs togenerate the first CSI-RS. The plurality of REs are distributed in theplurality of resource units. In each resource unit, a plurality of REsused to carry the first CSI-RS are located on the plurality ofsubcarriers in the same symbol, and the values of the first CSI-RScarried on the at least two REs in the resource unit are different.

According to a second aspect, a reference signal receiving method isprovided. The method includes: receiving, by a terminal device on aplurality of resource units, signals sent by a network device, where thesignals include a first CSI-RS; determining, by the terminal device, aplurality of resource elements (REs) used to carry the first CSI-RS,where the plurality of REs are distributed in a plurality of resourceunits, and in each resource unit, a plurality of REs used to carry thefirst CSI-RS are located on a plurality of subcarriers in a same symbol,values of the first CSI-RS carried on at least two REs are different,and values of the first CSI-RS are loaded to the plurality of REs in theresource unit by using a first multiplex code; and obtaining, by theterminal device, the first CSI-RS on the plurality of REs.

The first CSI-RS may be selected from a first pilot sequence generatedby the network device in advance. In other words, the first CSI-RSincludes some or all sequence elements in the first pilot sequence. Inthis embodiment of the present invention, each sequence element in apilot sequence may be referred to as a value of a CSI-RS, and a quantityof sequence elements in the pilot sequence may be referred to as asequence length of the pilot sequence. Correspondingly, a quantity ofdifferent CSI-RS values of a CSI-RS at each antenna port in each symbolin each resource unit is referred to as a sequence length of the CSI-RSat the antenna port in the symbol in the resource unit. It may beunderstood that, each CSI-RS value corresponds to a sequence element inthe pilot sequence, and different CSI-RS values correspond to differentsequence elements in the pilot sequence. In the prior art, a pluralityof REs in a same symbol in a same resource unit carry a same CSI-RSvalue. This is, a CSI-RS at each antenna port has a symbol length of 1in one symbol in one resource unit. However, in this embodiment of thepresent invention, a CSI-RS at each antenna port has a sequence lengthof at least 2 in each symbol in each resource unit. Compared with theprior art, the sequence length is increased and correlation betweensequences is reduced. Therefore, when two network devices send CSI-RSsby using a same time-frequency resource and a same multiplex code,because the CSI-RS provided in this embodiment of the present inventionis used, a sequence length in a same symbol in each resource unit isincreased, and correlation between sequences is reduced, so thatinterference between the two CSI-RSs is reduced, thereby facilitatingchannel estimation and improving quality of a received signal.

According to a third aspect, a network device is provided. The networkdevice includes various modules configured to perform the referencesignal sending method according to any one of the first aspect or thepossible implementations of the first aspect.

According to a fourth aspect, a terminal device is provided. Theterminal device includes various modules configured to perform thereference signal receiving method according to any one of the secondaspect or the possible implementations of the second aspect.

According to a fifth aspect, a network device is provided. The networkdevice includes a transceiver, a processor, and a memory. The processoris configured to control the transceiver to receive or send a signal,the memory is configured to store a computer program, and the processoris configured to invoke the computer program from the memory and run thecomputer program, to enable the network device to perform the methodaccording to any one of the first aspect or the possible implementationsof the first aspect.

According to a sixth aspect, a terminal device is provided. The terminaldevice includes a transceiver, a processor, and a memory. The processoris configured to control the transceiver to receive or send a signal,the memory is configured to store a computer program, and the processoris configured to invoke the computer program from the memory and run thecomputer program, to enable the terminal device to perform the methodaccording to any one of the second aspect or the possibleimplementations of the second aspect.

According to a seventh aspect, a computer program product is provided.The computer program product includes computer program code, and whenrunning on a network device, the computer program code enables thenetwork device to perform the method according to any one of the firstaspect or the possible implementations of the first aspect.

According to an eighth aspect, a computer program product is provided.The computer program product includes computer program code, and whenrunning on a terminal device, the computer program code enables theterminal device to perform the method according to any one of the secondaspect or the possible implementations of the second aspect.

According to a ninth aspect, a computer readable medium is provided. Thecomputer readable medium stores program code, and the program codeincludes an instruction used to perform the method according to any oneof the first aspect or the possible implementations of the first aspect.

According to a tenth aspect, a computer readable medium is provided. Thecomputer readable medium stores program code, and the program codeincludes an instruction used to perform the method according to any oneof the second aspect or the possible implementations of the secondaspect.

Optionally, the values of the first CSI-RS carried on the plurality ofREs in each resource unit are different from each other. Optionally, theplurality of REs carry a second CSI-RS, values of the second CSI-RScarried on at least two REs are different, and values of the secondCSI-RS are loaded to the plurality of REs by using a second multiplexcode.

In other words, when sending a plurality of CSI-RSs, the network devicemay determine values of the CSI-RSs in a first pilot sequence generatedin advance, map the values onto a time-frequency resource, load thevalues by using a multiplex code to distinguish between antenna ports,and finally send the plurality of CSI-RSs together by using thetime-frequency resource. For example, the plurality of CSI-RSs include afirst CSI-RS and a second CSI-RS, and the first CSI-RS and the secondCSI-RS correspond to different antenna ports and may be multiplexed on asame time-frequency resource through code division.

Optionally, the first pilot sequence is calculated by using thefollowing formulas:

r _(l,n) _(s) (b)=g(b), b=0, 1, . . . , N−1

where N=f(a, N_(RB) ^(max,DL)), a is a first parameter, N_(RB) ^(max,DL)represents a maximum quantity of resource units included on a downlinkchannel, and r_(l,n) _(s) (b) represents a value of a b^(th) CSI-RS inan l^(th) symbol in an n_(s) ^(th) slot.

${{r_{1,n_{s}}(b)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2b} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2b} + 1} \right)}}} \right)}}},\; {b = 0},1,\ldots,\; {N - 1}$

where c is a pseudo-noise (PN) sequence, and may be generated by a PNsequence generator (for example, a Gold sequence generator) based on aninitialization sequence c_(init).

This method is similar to a PN sequence generation formula defined in anexisting Long Term Evolution (LTE) protocol and therefore is very muchcompatible with the prior art, and in addition, a sequence length isincreased and correlation between pilot sequences is reduced.

Optionally, the first pilot sequence is calculated by using thefollowing formula:

r _(l,n) _(s) (m, n)=h(m, n), m=0, 1, . . . , N _(RB) ^(max,DL)−1, n=0,1, . . . , a−1

where a is a first parameter, N_(RB) ^(max,DL) represents a maximumquantity of resource units included on a downlink channel, and r_(l,n)_(s) (m, n) represents a value of an n^(th) CSI-RS in an m^(th) resourceunit in an l^(th) symbol in an n_(s) ^(th) slot.

For example, the first pilot sequence is calculated by using thefollowing formula:

${{r_{l,n_{s}}\left( {m,n} \right)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\left( {{ma} + n} \right)} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\left( {{ma} + n} \right)} + 1} \right)}}} \right)}}},\mspace{20mu} {m = 0},1,\ldots \;,\; {N_{RB}^{\max,\; {DL}} - 1}$

Compared with the formula described above, this formula represents, inmore dimensions, an RE onto which each sequence element is mapped.

Optionally, a value of the first parameter a includes at least one ofthe following: a quantity of REs in one symbol in one resource unit; alength of an orthogonal code used by a CSI-RS port during frequencydomain code division multiplexing; or a quantity of REs occupied by aCSI-RS port in one symbol in one resource unit.

Optionally, the value of the first parameter a includes at least one of{2,4,8,12}.

In this embodiment of the present invention, the first parameter a maybe understood as a maximum quantity of REs that can be occupied by thefirst CSI-RS in each resource unit. In other words, a maximum quantityof subcarriers occupied by the first CSI-RS in a same symbol in eachresource unit is a. However, it should be noted that the quantity ofsubcarriers occupied by the first CSI-RS in the same symbol in theresource unit does not mean a sequence length of the first CSI-RS in theresource unit. The sequence length of the first CSI-RS needs to bedefined based on a quantity of different sequence elements in theresource unit.

Optionally, the first parameter a is preconfigured.

In other words, the first parameter a may be statically configured.

Optionally, the first parameter a is sent to the terminal device afterbeing determined by the network device.

In other words, the first parameter a may be semi-statically ordynamically configured.

According to this application, a sequence length of a CSI-RS at eachantenna port in each symbol in each resource unit may be increased, toreduce correlation between sequences and reduce interference betweenpilot signals.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a communications system to which areference signal sending method and a reference signal receiving methodare applied according to an embodiment of the present invention;

FIG. 2 is another schematic diagram of a communications system to whicha reference signal sending method and a reference signal receivingmethod are applied according to an embodiment of the present invention;

FIG. 3 is a schematic flowchart of a reference signal sending method ora reference signal receiving method according to an embodiment of thepresent invention;

FIG. 4 is a schematic diagram of a pilot pattern according to anembodiment of the present invention;

FIG. 5 is another schematic diagram of a pilot pattern according to anembodiment of the present invention;

FIG. 6 is still another schematic diagram of a pilot pattern accordingto an embodiment of the present invention;

FIG. 7 is yet another schematic diagram of a pilot pattern according toan embodiment of the present invention;

FIG. 8 is a schematic block diagram of a network device according to anembodiment of the present invention;

FIG. 9 is a schematic block diagram of a terminal device according to anembodiment of the present invention;

FIG. 10 is another schematic block diagram of a network device accordingto an embodiment of the present invention; and

FIG. 11 is another schematic block diagram of a terminal deviceaccording to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions of this application withreference to accompanying drawings.

For ease of understanding embodiments of the present invention, a CSI-RSin an LTE Protocol is briefly described first.

In a Long Term Evolution Advanced (LTE-A) system, to support amulti-antenna technology, a CSI-RS featuring low-density resourcedistribution is introduced since Release 10 to replace an originalcell-specific reference signal (CRS), to ensure that a network devicecan perform multi-user scheduling based on CSI reported by a terminaldevice.

In an LTE-A transmission mode (TM) 9, the terminal device uses a CSI-RSfor channel estimation. However, in other transmission modes prior tothe TM 9, the terminal device still uses a CRS for channel estimation.It may be understood that regardless of whether a CSI-RS or a CRS, oreven other reference signals that are used for channel estimation andthat are defined in future protocols are used, specific processes inwhich the terminal device performs channel estimation based on areceived reference signal may be similar. For ease of understanding anddescription, the embodiments of the present invention are described indetail by using a CSI-RS only as an example.

In addition, in a downlink reference signal, the reference signal mayusually use a pseudo-noise (PN) sequence. In LTE, a CSI-RS may begenerated based on a PN sequence. Specifically, the CSI-RS may beobtained by using the PN sequence that is calculated by using thefollowing formula (formula (1)):

${{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots,\; {N_{RB}^{\max,{DL}} - 1}$

with

c _(init)=2¹⁰·(7·(n′ _(s)+1)+l+1)·(2·N _(ID) ^(CSI)+1)+2·N _(ID) ^(CSI)+N _(CP)

When the CSI-RS is used as a part of a discovery reference signal (DRS),n′_(s)=10└n_(s)/10┘+n_(s) mod 2; or in other cases, n′_(s)=n_(s·)r_(l,n)_(s) (m) represents an m^(th) sequence element in an l^(th) symbol in ann_(s) ^(th) slots, and r_(l,n) _(s) (m) is displayed in a complex formobtained by modulating a PN sequence. Optionally, the symbol may be anOFDM symbol, or may be a symbol that is used to represent a time unitand that is defined in a future protocol. This is not particularlylimited in this embodiment of the present invention. N_(RB) ^(max,DL)represents a maximum quantity of RBs included on a downlink channel. cis a PN sequence, and may be generated by a PN sequence generator (forexample, a Gold sequence generator) based on an initialization sequencec_(init). N_(ID) ^(CSI) is an identifier of a CSI-RS, and may be a cellidentifier N_(ID) ^(cell) or an identifier configured by a higher layer.N_(CP) is a cyclic suffix identifier and corresponds to a normal CP, andN_(CP)=1. For an extended CP, N_(CP)=0.

It may be learned from the foregoing formula that, when [O, N_(RB)^(max,DL)−1] is traversed for a value of m, a PN sequence can beobtained. The PN sequence includes N_(RB) ^(max,DL) sequence elements,each sequence element is a complex signal, each sequence element may bereferred to as a value of the CSI-RS, and the N_(RB) ^(max,DL) sequenceelements may be referred to as a sequence length N_(RB) ^(max,DL).

The network device may map, based on a predefined pilot pattern and amapping relationship between sequence elements in a pilot sequence andREs, some or all elements in the generated PN sequence onto the REs oneby one, and send a CSI-RS to the terminal device over a channel. Theterminal device estimates a channel matrix based on the received CSI-RSand a CSI-RS generated by the terminal device, so that the terminaldevice can determine a precoding matrix based on the estimated channelmatrix, and feed back CSI to the network device.

In LTE, as the multi-antenna technology develops, a same network devicemay distinguish between different antenna ports through CDM, frequencydivision multiplexing (FDM), time division multiplexing (TDM), and thelike. If FDM or TDM is used, frequency domain resources or time domainresources occupied by CSI-RSs at different antenna ports may bedifferent. If CDM is used, time-frequency resources occupied by CSI-RSsat different antenna ports may be the same, and the different antennaports are distinguished by using a multiplex code. In LTE, CDM mayinclude frequency domain CDM and time domain CDM. However, in NR, theCSI-RSs are supported to be configured in a same symbol, in other words,frequency domain CDM.

It should be noted that, an antenna port may also be referred to as aCSI-RS port, or more specifically, may be understood as a CSI-RS portthat has not been precoded through beamforming. The CSI-RS is defined bythe CSI-RS port, and each CSI-RS corresponds to an antenna port. Itshould be understood that, the CSI-RS, as a reference signal used forchannel measurement, is merely used as an example for description andshould not be constructed as any limitation on the embodiments of thepresent invention. This application does not exclude a possibility thatin an existing or a future protocol, other names may be used to replaceCSI-RS to implement a same function of the CSI-RS.

A scenario to which the embodiments of the present invention areapplicable is described below with reference to FIG. 1 and FIG. 2. FIG.1 is a schematic diagram of a communications system 100A to which areference signal sending method and a reference signal receiving methodare applied according to an embodiment of the present invention. Asshown in FIG. 1, the communications system 100A includes a first networkdevice 110, a second network device 120, a first terminal device 130,and a second terminal device 140. The first network device 110 and thesecond network device 120 may include a plurality of antennas, andtransmit data to a terminal device (for example, the first terminaldevice 130 and/or the second terminal device 140 shown in FIG. 1) byusing a multi-antenna technology.

It is assumed that the first network device 110 is a network device in afirst cell, and the first terminal device 130 is located in the firstcell; and the second network device 120 is a network device in a secondcell, and the second terminal device is located in the second cell. Ifthe first network device 110 and the second network device 120 sendCSI-RSs to the corresponding first terminal device 130 and secondterminal device 140 by using a same port and a same time-frequencyresource (for example, an RE), to obtain a CSI fed back for channelestimation, the CSI-RS (for example, denoted as a CSI-RS #1) sent by thefirst network device 110 to the first terminal device 130 and the CSI-RS(for example, denoted as a CSI-RS #2) sent by the second network device120 to the second terminal device 140 may be identified by usingdifferent N_(ID) ^(CSI), in other words, values calculated by using theformula (1) are different.

Because the first network device 110 and the second network device 120may transmit data with the terminal device by using the multi-antennatechnology, the first network device 110 and the second network device120 may send the CSI-RSs by using a plurality of antenna ports. At theplurality of antenna ports in a same network device, different CSI-RSsmay be distinguished through FDM, TDM or CDM described above.

If both the first network device 110 and the second network device 120use frequency domain CDM (which may be, for example, frequency domainCDM2), a quantity of REs occupied by each CSI-RS in one symbol in oneresource block group (RBG) in a resource unit (for example, a resourceblock (RB)) is a length of an orthogonal code used during the CDM. Forexample, frequency domain CDM2 indicates that two REs are occupied inone symbol in one resource unit. It can be learned according to theabove-described formula (1) that, when symbol quantities l are the sameand values of r are the same, values of the CSI-RSs carried on the twoREs are the same. This is, a sequence length of the CSI-RS in one symbolin one resource unit is 1. Even though the CSI-RS #1 and CSI-RS #2 usedifferent N_(ID) ^(CSI), interference is still caused between the CSI-RS#1 and CSI-RS #2 because other parameters (for example, OCCs) are thesame.

FIG. 2 is a schematic diagram of a communications system 100B to which areference signal sending method and a reference signal receiving methodare applied according to an embodiment of the present invention. Asshown in FIG. 2, the communications system 100B includes a first networkdevice 110, a second network device 120, and a first terminal device130. The first network device 110 and the second network device 120 mayinclude a plurality of antennas, and transmit data to the first terminaldevice 130 by using a multi-antenna technology. Moreover, the firstnetwork device 110 and the second network device 120 may transmit datato the first terminal device 130 by using a coordinated multipoint(CoMP) transmission method.

Assuming that the first network device 110 sends a CSI-RS #1 to thefirst terminal device 130, and the second network device 120 sends aCSI-RS #2 to the first terminal device 130, the first network device 110and the second network device 120 may perform dynamic point selection(DPS) based on CSI fed back by the first terminal device 130. The CSI-RS(for example, denoted as the CSI-RS #1) sent by the first network device110 to the first terminal device 130 and the CSI-RS (for example,denoted as the CSI-RS #2) sent by the second network device 120 to thefirst terminal device 130 may be identified by using different N_(ID)^(CSI).

If both the first network device 110 and the second network device 120use frequency domain CDM, a quantity of REs, occupied by the CSI-RS sentby each network device, in one symbol in one resource unit is a lengthof an orthogonal code used during the CDM. REs that carry CSI-RSs in asame symbol carry a same CSI-RS value, in other words, a sequence lengthof a CSI-RS in one symbol in one resource unit is 1. Therefore, eventhough the CSI-RS #1 and CSI-RS #2 use different N_(ID) ^(CSI),interference is still caused between the CSI-RS #1 and CSI-RS #2 becauseother parameters (for example, antenna ports, time-frequency resources,and OCCs) are the same.

It should be understood that, FIG. 1 and FIG. 2 are simplified schematicdiagrams used as an example for ease of understanding, and thecommunications system may further include more network devices and/orterminal devices that are not shown in the figure.

It can be learned from the foregoing description that, when interferenceis caused between two CSI-RSs, estimation on a channel matrix may beinaccurate, and consequently, accuracy of a CSI fed back is affected,determining of a precoding matrix may finally be affected, furtheraffecting quality of received data.

However, it is found through a simulation experiment or calculation oncorrelation that, when the sequence length is 1, correlation betweensequences is relatively strong; and a longer sequence indicates lowercorrelation between the sequences. Therefore, this application providesa reference signal sending method and a reference signal receivingmethod, to increase a sequence length of a pilot sequence correspondingto each port in a symbol, reduce correlation between sequences, andreduce interference.

Embodiments of the present invention are described in detail below withreference to the accompanying drawings.

It should be understood that, technical solutions in this applicationmay be applied to various communications systems, for example, a GlobalSystem for Mobile communications (GSM), a Code Division Multiple Access(CDMA) system, a Wideband Code Division Multiple Access (WCDMA) system,a general packet radio service (GPRS), a Long Term Evolution (LTE)system, a Long Term Evolution Advanced (LTE-A) system, a UniversalMobile Telecommunications System (UMTS), or a next-generationcommunications system (for example, a fifth-generation (5G)communications system). The 5G system may also be referred to as a newradio access technology (NR) system.

This application describes the embodiments with reference to a networkdevice. The network device may be a base transceiver station (BTS) inGlobal System for Mobile communications (GSM) or Code Division MultipleAccess (CDMA), or may be a NodeB (NB) in Wideband Code Division MultipleAccess (WCDMA), or may be an evolved NodeB (evolved node B, eNB oreNodeB) in Long Term Evolution (LTE), or a relay station, an accesspoint or a remote radio unit (RRU), or an in-vehicle device, a wearabledevice, or a network side device in a future 5G system such as atransmission point (TP), a transmission reception point (TRP), a basestation, and a small base station device. This is not particularlylimited in embodiments of the present invention.

In addition, this application describes embodiments with reference to aterminal device. The terminal device may also be referred to as userequipment (UE), an access terminal, a subscriber unit, a subscriberstation, a mobile station, a mobile console, a remote station, a remoteterminal, a mobile device, a user terminal, a terminal, a wirelesscommunications device, a user agent, or a user apparatus. The terminaldevice may be a station (ST) in a wireless local area network (WLAN),may be a cellular phone, a cordless phone, a Session Initiation Protocol(SIP) phone, a wireless local loop (WLL) station, a personal digitalassistant (PDA) device, a handheld device having a wirelesscommunication function, a computing device, another processing deviceconnected to a wireless modem, an in-vehicle device, a wearable device,and a next generation communication system, for example, a terminaldevice in a 5G network, or a terminal device in a future evolved publicland mobile network (PLMN). This is not particularly limited inembodiments of this application.

It should be further understood that, in embodiments of the presentinvention, numbers “first” and “second” are merely used to distinguishbetween different objects, for example, to distinguish between differentpilot sequences and different CSI-RSs, and should not be constructed asany limitation on the embodiments of the present invention.

FIG. 3 is a schematic flowchart of a reference signal sending orreference signal receiving method 300 according to an embodiment of thepresent invention from the perspective of device interaction. The method300 described below may be applied to a communications system thatperforms communication by using a radio air interface. Thecommunications system may include at least two network devices and atleast one terminal device. For example, the communications system may bethe communications system 100A shown in FIG. 1, or the communicationssystem 100B shown in FIG. 2. The network device may be the first networkdevice 110 or the second network device 120 shown in FIG. 1 or FIG. 2,and the terminal device may be the first terminal device 130 or thesecond terminal device 140 shown in FIG. 1, or the first terminal device130 shown in FIG. 2.

It should be noted that, in this embodiment of the present invention,without loss of generality, the reference signal sending method and thereference signal receiving method according to this embodiment of thepresent invention are described in detail by using a CSI-RS as anexample. However, it should be understood that this should not beconstructed as any limitation on this embodiment of the presentinvention, and the method is also applicable to other reference signals.

It should be understood that in an existing protocol (for example, anLTE protocol), a downlink reference signal may usually use a PNsequence, and in LTE, the PN sequence is defined by a Gold sequence. Forease of understanding and description only, this specification describesthis embodiment of the present invention in detail by using the PNsequence as an example. However, this should not be constructed as anylimitation on this embodiment of the present invention, and thisapplication does not exclude a possibility that another sequence such asa Zadoff-Chu (ZC) sequence may be used in a future protocol to generatea downlink reference signal. Moreover, the reference signal sendingmethod and the reference signal receiving method according to thisembodiment of the present invention are not limited to a downlinkreference signal, and are also applicable to an uplink reference signal.

As shown in FIG. 3, the method 300 includes the following steps.

S310. A network device generates a first pilot sequence based on a firstparameter.

In this embodiment of the present invention, a sequence length of a PNsequence used to generate a CSI-RS is not only correlated to N_(RB)^(max,DL), but also correlated to the first parameter a provided in thisembodiment of the present invention. The network device may generate thefirst pilot sequence based on the first parameter a. Herein, for ease ofdistinguishing and description, a pilot sequence generated by thenetwork device is denoted as the first pilot sequence, and a pilotsequence generated by a terminal device described below is denoted as asecond pilot sequence. Correspondingly, a CSI-RS generated by thenetwork device based on the first pilot sequence is denoted as a firstCSI-RS, and a CSI-RS generated by the terminal device based on thesecond pilot sequence is denoted as a third CSI-RS.

Optionally, a value of the first parameter a includes at least one ofthe following:

A. A quantity of REs in one symbol in one resource unit. A specificquantity may be determined based on a definition of the resource unit inthe existing or the future protocol. For example, the resource unitdefined in an LTE protocol may be an RB, and a quantity of REs in onesymbol in one RB may be 12.

In this embodiment of the present invention, the resource unit may beone RB or RBG or a plurality of RBs or RBGs in the LTE protocol, or aredefined resource including at least two REs. For ease of understandingand description, this embodiment of the present invention is describedby using an example in which a resource unit is an RB. For brevity, sameor similar cases are omitted below.

B. A length of an orthogonal code used by an antenna port duringfrequency domain CDM. A specific value may be determined based on alength that is of an orthogonal code for CDM and that is defined in theexisting or future protocol. For example, in the LTE protocol, CDM2 andCDM4 are defined, and therefore, the value of a may be any value in{2,4}.

C. A quantity of REs occupied by an antenna port in a symbol. A specificvalue may be determined based on a pilot pattern. For example, in theLTE protocol, when CDM4 is used, a quantity of REs occupied by anantenna port in one symbol in one RB may be 2. In NR, assuming that theresource unit is an RB, a density of the CSI-RS may be the same as thatin LTE, in other words, equal to 1 RE/port/RB, or may be greater than 1RE/port/RB. Then, the quantity of REs occupied by an antenna port in onesymbol in one RB is equal to a frequency domain CDM value multiplied bythe density. However, it may be understood that the quantity of REsoccupied by one antenna port in one symbol does not exceed a quantity ofsubcarriers in one RB (for example, the quantity of subcarriers in oneRB is 12). The value of a may be 2, 4, 8, or 12.

In conclusion, the value of the first parameter a may be at least one of{2,4,8,12}.

It should be understood that the above-listed specific values of thefirst parameter a are described only as an example, or may be possiblevalues provided in this embodiment of the present invention. However,this should not be constructed as any limitation on this embodiment ofthe present invention. Any method for generating a pilot sequence bydefining the first parameter a to increase the sequence length shallfall within the protection scope of this application, and thisapplication does not exclude a possibility that more values may bedefined for the first parameter a in the future protocol.

Moreover, the first parameter a may have one value, or may have aplurality of values. The value or values may be statically configured,or may be semi-statically configured or dynamically configured.

Specifically, when the first parameter a has one value, the firstparameter may be configured at least by using the following two methods:

Method 1: The first parameter a is preconfigured. Specifically, thevalue of the first parameter a may be stipulated in a protocol. Theparameter may be configured for the network device and the terminaldevice respectively to generate a pilot sequence. In this case, it maybe considered that the first parameter a is statically configured.

Alternatively, a defining rule of the first parameter a may bestipulated in a protocol, and the defining rule of the first parameter ais configured in the network device and the terminal devicerespectively, so that the network device and the terminal devicedetermine the first parameter according to the same defining rule. Forexample, a mapping relationship between the first parameter and a CDMorthogonal code length may be defined in the protocol, and when the CDMorthogonal code length is determined, the corresponding first parametera may be determined based on the foregoing mapping relationship. In thiscase, it may be considered that the first parameter a is semi-staticallyconfigured.

Method 2: The network device determines the first parameter a, and sendsthe first parameter a to the terminal device.

Specifically, the network device may determine the first parameter abased on factors such as the CDM orthogonal code length and a CSI-RSdensity, and notifies the terminal device of the first parameter athrough signaling. In this case, the first parameter a may besemi-statically configured or dynamically configured.

Optionally, the network device sends a Radio Resource Control (RRC)message to the terminal device, and the RRC message carries the firstparameter a.

Optionally, the network device sends a Media Access Control (MAC)control element (CE) to the terminal device, and the MAC-CE carries thefirst parameter a.

Optionally, the network device sends a physical downlink control channel(PDCCH) to the terminal device, and the PDCCH carries the firstparameter a. Specifically, the first parameter may be carried indownlink control information (DCI) on the PDCCH.

It should be understood that the above-listed signaling used for sendingthe first parameter is described only as an example, and should not beconstructed as any limitation on this embodiment of the presentinvention, and this embodiment of the present invention should not belimited thereto, either. Any signaling that can carry the firstparameter should fall within the protection scope of this application.

When the first parameter a has a plurality of values, the firstparameters a may be semi-statically configured or dynamicallyconfigured. In this case, the first parameters a may also be configuredby using the foregoing methods.

Specifically, the plurality of first parameters a may be carried byusing an RRC message, and then a first parameter a used in a currentsubframe is indicated by using DCI. It may be understood that, thecurrently used first parameter a is any one of the plurality of firstparameters a.

After the first parameter a is determined, the network device maygenerate the first pilot sequence based on the first parameter a.

Specifically, the network device may generate the first pilot sequenceby using any one of the following methods:

Method 1:

The network device may generate the first pilot sequence according tothe following formula:

r _(l,n) _(s) (b)=g(b), b=0, 1, . . . , N−1

where N=f(a, N_(RB) ^(max,DL)), and r_(l,n) _(s) (b) represents a valueof a b^(th) CSI-RS in an l^(th) symbol in an n_(s) ^(th) slot, and thevalue may be a function g(b) of b.

It may be learned that a sequence length of the first pilot sequence isN, and N is a function of the first parameter a and N_(RB) ^(max,DL).For example, N=a·N_(RB) ^(max,DL), N=2a·N_(RB) ^(max,DL), andN=a²·N_(RB) ^(max,DL), and for brevity, an example is not listed hereinagain. It should be understood that the above-listed f( ) form isdescribed only as an example, and should not be constructed as anylimitation on this embodiment of the present invention. All functions byusing which the pilot sequence length N is determined based on the firstparameter a, and the determined sequence length N is greater than theexisting pilot sequence length N_(RB) ^(max,DL) may fall within theprotection scope of this application.

For ease of understanding, a specific process of generating the firstpilot sequence is described with reference to r_(l,n) _(s) defined inthe LTE protocol. In this embodiment of the present invention, the firstpilot sequence is generated by using a PN sequence, and the PN sequencemay be obtained by using the following formula (formula (2)):

${{r_{l,n_{s}}(b)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2b} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2b} + 1} \right)}}} \right)}}},{b = 0},1,\ldots \;,{N - 1}$

Definitions of c, b, and N in the formula are described above, and arenot repeatedly described herein. In this embodiment of the presentinvention, a length of c is determined based on the sequence length N ofthe first pilot sequence, and may be, for example, twice the pilotsequence length N. N_(ID) ^(CSI) represents an identifier of a pilotsequence, and in this embodiment of the present invention, N_(ID) ^(CSI)may refer to a value in LTE or may be re-configured. N_(CP) represents acyclic prefix identifier, and in this embodiment of the presentinvention, N_(CP) may refer to a value in LTE or may be re-configured.

For ease of understanding and description, the process of generating thefirst pilot sequence by the network device according to the formula (2)is described in detail below by using N=a·N_(RB) ^(max,DL) as an examplewith reference to the above-listed values of the first parameter a.N_(RB) ^(max,DL) may be a maximum quantity of resource units included ina downlink bandwidth. For example, N_(RB) ^(max,DL) may be a maximumquantity of RBs included in a downlink bandwidth in the existing LTEprotocol, and N_(RB) ^(max,DL)=110.

It is assumed that the first parameter a is a quantity of REs in onesymbol in one RB. In LTE, the quantity of REs in one symbol in one RB,namely, a=12, so that the sequence length N of the first pilot sequenceis equal to 1320, and b=0, 1, . . . , 1319. 1320 sequence elements, inother words, r_(l,n) _(s) (0), r_(l,n) _(s) (1), r_(l,n) _(s) (1319),may be obtained by traversing a range of [0, 1319] for the value of a,each value of b corresponds to a sequence element, and each sequenceelement may be understood as a value of a CSI-RS.

For example, when b=0,

${{r_{l,n_{s}}(0)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2 \times 0} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2 \times 0} + 1} \right)}}} \right)}}};$and  when  ${b = 1},\; {{r_{l,n_{s}}(1)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2 \times 1} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {{c\left( {{2 \times 1} + 1} \right)}.}}} \right.}}}$

By analogy, 220 sequence elements may be obtained. For brevity, thesequence elements are not listed one by one herein.

Assuming that the first parameter a is at least one of 2, 4, 8, or 12,and using a=2 as an example, the sequence length N of the first pilotsequence is equal to 220, and b=0, 1, . . . , 219. The 220 sequenceelements, namely, r_(l,n) _(s) (0), r_(l,n) _(s) (1), r_(l,n) _(s) (219)may be obtained by traversing a range of [0, 219] for the value of a.Each value of b corresponds to a sequence element, and each sequenceelement may be understood as a value of a CSI-RS.

It is assumed that the first parameter a is a length of an orthogonalcode used by an antenna port during frequency domain CDM. Because in NR,CSI-RSs are configured in a same symbol, used CDM is frequency domainCDM. In LTE, CDM2 and CDM4 are defined. Using a=4 as an example, thesequence length N of the first pilot sequence is equal to 440, and b=0,1, . . . , 439. 440 sequence elements, namely, r_(l,n) _(s) (0), r_(l,n)_(s) (1), r_(l,n) _(s) (439), may be obtained by traversing a range of[0, 439] for the value of a. Each value of b corresponds to a sequenceelement, and each sequence element may be understood as a value of aCSI-RS.

The formula (2) in Method 1 is similar to a PN sequence generationformula defined in the existing LTE protocol and therefore is very muchcompatible with the prior art, and in addition, a sequence length isincreased and correlation between pilot sequences is reduced.

Method 2:

The network device may generate the first pilot sequence according tothe following formula:

r _(l,n) _(s) (m, n)=h(m, n), m=0, 1, . . . , N _(RB) ^(max,DL)−1, n=0,1, . . . , a−1

where N=f(a, N_(RB) ^(max,DL)), and r_(l,n) _(s) (b) represents a valueof an n^(th) CSI-RS in an m^(th) resource unit in an l^(th) symbol in ann_(s) ^(th) slot, and the value may be a function h(m, n) of m and n.The sequence length N of the first pilot sequence may be the same as thesequence length defined in Method 1, and for brevity, details are notdescribed herein again.

For ease of understanding, a specific process of generating the firstpilot sequence is described with reference to r_(l,n) _(s) defined inthe LTE protocol. In this embodiment of the present invention, the firstpilot sequence is generated by using a PN sequence, and the PN sequencemay be obtained by using the following formula (formula (3)):

${{r_{l,n_{s}}\left( {m,n} \right)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\left( {{ma} + n} \right)} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\left( {{ma} + n} \right)} + 1} \right)}}} \right)}}},\; \mspace{20mu} {m = 0},1,\ldots \;,{N_{RB}^{\max,{DL}} - 1}$

Definitions of c, m, n, and N in the formula are described above, andare not repeatedly described herein.

In Method 2, because a number m of the resource unit is substituted intothe PN sequence generation formula (in other words, the formula (3)),sequence elements in each resource unit are more specifically limited.

For ease of understanding, the process of generating the first pilotsequence by the network device according to the formula (3) is describedin detail below still by using N=a·N_(RB) ^(max,DL) as an example withreference to the above-listed values of the first parameter a. N_(RB)^(max,DL) may be a maximum quantity of resource units included in adownlink bandwidth. For example, N_(RB) ^(max,DL) may be a maximumquantity of RBs included in a downlink bandwidth in the existing LTEprotocol, and N_(RB) ^(max,DL)=110.

It is assumed that the first parameter a is a quantity of REs in onesymbol in one RB. In LTE, the quantity of REs in one symbol in one RB,namely, a=12, so that the sequence length N of the first pilot sequenceis equal to 1320, and b=0, 1, . . . , 1319. A value of m is 0, 1, . . ., or N_(RB) ^(max,DL)−1, in other words, a range of [0, 109] istraversed for the value of m. Because the sequence length N=a·N_(RB)^(max,DL), a value of n is 0, 1, . . . , or a-1, in other words, a rangeof [0, 11] is traversed for the value of n. In other words, each time avalue is selected for m, the range of [0, 11] is traversed for n.

For example, when m=0, n=0, 1, . . . , or 11.

${r_{l,n_{s}}\left( {0,0} \right)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\left( {{12 \times 0} + 0} \right)} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\left( {{12 \times 0} + 0} \right)} + 1} \right)}}} \right)}}$${r_{l,n_{s}}\left( {0,1} \right)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2\left( {{12 \times 0} + 1} \right)} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\left( {{12 \times 0} + 1} \right)} + 1} \right)}}} \right)}}$

By analogy, 12 sequence elements may be obtained when m=0. For brevity,the sequence elements are not listed one by one herein. Then, when m=1,2, . . . , or 109, the range of [0, 11] is traversed for the value of n,and 12 sequence elements may be obtained. When the first parameter a hasdifferent values, the network device may still generate correspondingsequence elements according to the foregoing method. For brevity,examples are not described herein one by one.

In other words, each value of m corresponds to a resource unit, and whenthe value of m is given, each value of n corresponds to a sequenceelement in an RB. A difference between the formula (3) in Method 2 andthe formula (2) in Method 1 lies in that an RE onto which each sequenceelement is mapped is limited in more dimensions.

It should be noted that although the formulas for generating the firstpilot sequence in Method 1 and Method 2 are different, when the firstparameter is given, sequence elements of pilot sequences generatedaccording to Method 1 and Method 2 are the same, and sequence lengths ofthe pilot sequences are also the same. The pilot sequences are obtainedby using different calculation methods of Method 1 and Method 2. Inaddition, this embodiment of the present invention does not exclude apossibility that the first pilot sequence may be generated by usinganother possible formula, so that an obtained pilot sequence length isgreater than a pilot sequence length in the prior art.

S320. The network device determines a plurality of REs used to carry afirst CSI-RS, and values of the first CSI-RS are selected from the firstpilot sequence.

It should be noted that the network device may send, by using aplurality of antenna ports, CSI-RSs to one or more terminal devices forchannel measurement. When sending the plurality of CSI-RSs, the networkdevice may determine values of the CSI-RSs in the generated first pilotsequence, map the values onto a time-frequency resource, load the valuesby using a multiplex code to distinguish between antenna ports, andfinally send the plurality of CSI-RSs together by using thetime-frequency resource. In this embodiment of the present invention,for ease of distinguishing and description, a specific process ofsending a CSI-RS by the network device is described in detail by usingthe CSI-RS (for example, denoted as the first CSI-RS) that is sent bythe network device by using a first antenna port as an example. However,this should not be constructed as any limitation on this embodiment ofthe present invention, and it does not mean that the plurality of REs onwhich the first CSI-RS is located are used to send the first CSI-RSonly, and the plurality of REs used to carry the first CSI-RS can alsocarry a CSI-RS of another antenna port, for example, a CSI-RS (forexample, denoted as a second CSI-RS) of a second antenna port. It may beunderstood that, values of the first CSI-RS and the second CSI-RScarried on a same RE are selected from a same sequence element in thefirst pilot sequence, in other words, values of the first CSI-RS and thesecond CSI-RS carried on a same RE may be the same. The first CSI-RS andthe second CSI-RS that have a same value may be multiplexed on a sametime-frequency resource through code division. Moreover, the firstCSI-RS and the second CSI-RS may be CSI-RSs sent to a same terminaldevice, or may be CSI-RSs sent to different terminal devices. This isnot particularly limited in this embodiment of the present invention.

Herein, without loss of generality, this embodiment of the presentinvention is described in detail by using the process of sending thefirst CSI-RS by the network device as an example. It may be understoodthat a specific process of sending CSI-RSs by the network device byusing different antenna ports is the same as the specific process ofsending the first CSI-RS by the network device.

After generating the first pilot sequence in S310, the network devicemay determine a currently used pilot pattern based on the firstparameter of the CSI-RS, determine the plurality of REs used to carrythe first CSI-RS based on a mapping relationship between sequenceelements and REs in the pilot pattern, and map some or all sequenceelements in the first pilot sequence (in other words, the plurality ofvalues of the first CSI-RS) onto the plurality of REs.

It should be noted that, the method for generating the first pilotsequence by the network device may be the method of S310 described abovein this embodiment of the present invention, or may refer to a pilotsequence generation method in the prior art, and S310 is used as anoptional step. In other words, a possible implementation for generatingthe first pilot sequence should not be constructed as any limitation onthis embodiment of the present invention, and this embodiment of thepresent invention should not be limited thereto, either.

In this embodiment of the present invention, if the first pilot sequenceis obtained through step S310, a mapping relationship between a sequenceelement and an RE may be reflected by using the mapping relationshipbetween b and an RE in S310, or the mapping relationship between m, nand an RE. For example, a b^(th) sequence element is mapped onto an REin a resource unit, or an n^(th) sequence element in an m^(th) resourceunit is mapped onto an RE in the m^(th) resource unit.

It should be noted that, the pilot pattern and the mapping relationshipbetween a sequence element and an RE may be preconfigured, or themapping relationship may be determined by referring to a mapping rulebetween a pilot element and an RE in the prior art. The pilot patternand the mapping relationship between a sequence element and an RE arenot particularly limited in this embodiment of the present invention.

In this embodiment of the present invention, the plurality of REs usedto carry the first CSI-RS may be distributed in a plurality of resourceunits. In each resource unit, a plurality of REs used to carry the firstCSI-RS are located on a plurality of subcarriers in a same symbol.Moreover, in the plurality of REs in the same resource unit, values ofthe first CSI-RS carried on at least two REs are different, and thevalues of the first CSI-RS may be loaded to the plurality of REs in theresource unit by using a first multiplex code (for ease ofdistinguishing, a multiplex code corresponding to the first antenna portis denoted as the first multiplex code).

In other words, for each resource unit, the network device may select atleast two different sequence elements from the first pilot sequencegenerated in S310 and map the sequence elements onto REs. Therefore, asequence length of the first CSI-RS in each symbol in each resource unitis greater than or equal to 2.

A quantity of a plurality of subcarriers that are in a same symbol andon which the plurality of REs used to carry the first CSI-RS in eachresource unit are located is a quantity of REs occupied by the firstCSI-RS in the resource unit. Optionally, the quantity of the pluralityof subcarriers that are in the same symbol and on which the plurality ofREs used to carry the first CSI-RS in the resource unit are located maybe any value in {2,4,8,12}. In other words, in each resource unit, thequantity of REs occupied by the first CSI-RS may be 2, 4, 8, or 12.However, it should be noted that this does not mean that the sequencelength of the first CSI-RS in each resource unit is 2, 4, 8, or 12. Thesequence length of the first CSI-RS needs to be defined based on aquantity of different sequence elements in the resource unit. It shouldbe understood that, the plurality of REs in each resource unit may becontinuous or discontinuous in frequency domain. This is notparticularly limited in this embodiment of the present invention.

Optionally, the values of the first CSI-RS carried on the plurality ofREs in each resource unit are different from each other.

In other words, values of the first CSI-RS carried on any two of theplurality of REs in each resource unit are different.

In other words, if the values of the first CSI-RS carried on theplurality of REs in each resource unit are different from each other,and the first CSI-RS occupies s (s≥2, and s is a natural number) REs inthe resource unit, the sequence length of the first CSI-RS in theresource unit is s.

For example, if the first CSI-RS occupies 12 REs in each RB (in otherwords, an example of the resource unit), and values of the first CSI-RScarried on the 12 REs are different from each other, the first CSI-RSfully occupies 12 subcarriers in a symbol. Corresponding to the formula(2) described above, the network device selects 12 different values forb (specific values of b may be determined based on a predefined mappingrelationship between a sequence element and an RE), and obtains 12different sequence elements. Alternatively, corresponding to the formula(3) described above, the network device may determine the value of mbased on a number of a current RB, traverse the range of [0, 11] for thevalue of n, and obtain 12 different sequence elements. The networkdevice maps the 12 sequence elements one by one onto 12 subcarriers in asame symbol based on the predefined mapping relationship. In this case,the first CSI-RS and another CSI-RS (for example, the second CSI-RS) mayimplement code division multiplexing by using 6 sets of OCC codes havinga length of 2.

For another example, if the first CSI-RS occupies two REs in each RB,values of the first CSI-RS carried on the two REs are definitelydifferent, and then the first CSI-RS occupies two subcarriers in asymbol. It should be noted that the first CSI-RS occupies two REs ineach RB. This does not mean that the value of the first parameter a ofthe first pilot sequence is 2, and the first parameter a may be 2 or maybe a natural number greater than 2.

For ease of understanding this embodiment of the present invention, thefollowing describes correspondences between different antenna portquantities and pilot patterns with reference to the accompanyingdrawings.

Assuming that an antenna port quantity is 2, the network devicedetermines that a CSI-RS corresponding to each antenna port may occupytwo REs in each RB (namely, an example of the resource unit).

FIG. 4 and FIG. 5 are schematic diagrams of pilot patterns according toan embodiment of the present invention. Specifically, FIG. 4 and FIG. 5show possible pilot patterns of CSI-RSs when an antenna port quantity is2. As shown in FIG. 4, two REs used to carry a first CSI-RS may bedistributed in a same symbol. For example, two REs used to carry thefirst CSI-RS shown in the figure are located in a symbol #5, and the twoREs are located on a subcarrier #10 and a subcarrier #11. As shown inFIG. 5, the two REs used to carry the first CSI-RS may be distributed ina same symbol, for example, the symbol #5 shown in the figure, and thetwo REs are located on a subcarrier #8 and a subcarrier #9. By analogy,the two REs used to carry the first CSI-RS may be located on any twosubcarriers located in a same symbol, for example, a subcarrier #6 and asubcarrier #7, and a subcarrier #4 and a subcarrier #5 which are notshown in the figure. Moreover, the CSI-RSs at the two antenna ports maybe distinguished by using a multiplex code, in other words, frequencydomain CDM is implemented.

As to a first pilot sequence, values of the first CSI-RS carried on thetwo REs correspond to different values of b in the formula (2), orcorrespond to different values of m and n in the formula (3).

If a=2, corresponding to the formula (2) described above, the networkdevice selects two different values for b (specific values of b may bedetermined based on a predefined mapping relationship between a sequenceelement and an RE), and obtains two different sequence elements.Alternatively, corresponding to the formula (3) described above, thenetwork device may determine the value of m based on a number of acurrent RB, select values 0 and 1 for n, and obtain two differentsequence elements. The network device maps the two sequence elements oneby one onto two subcarriers in a same symbol based on the predefinedmapping relationship.

If a=12, corresponding to the formula (2) described above, the networkdevice selects two different values for b (specific values of b may bedetermined based on a predefined mapping relationship between a sequenceelement and an RE). For example, the network device may select a valuebased on a number of a subcarrier of an occupied RE, and obtain twodifferent sequence elements. Alternatively, corresponding to the formula(3) described above, the network device may determine the value of mbased on a number of a current RB, and select two values for n from [0,11]. For example, the network device may select a value based on anumber of a subcarrier of an occupied RE, and obtain two differentsequence elements. The network device maps the two sequence elements oneby one onto two subcarriers in a same symbol based on the predefinedmapping relationship.

If a=4 or 8, corresponding to the formula (2) described above, thenetwork device selects two different values for b (specific values of bmay be determined based on a predefined mapping relationship between asequence element and an RE), and obtains two different sequenceelements. Alternatively, corresponding to the formula (3) describedabove, the network device may determine the value of m based on a numberof a current RB, select two values, for example, select any two values,for n from [0, 3] or [0, 7], and obtain two different sequence elements.The network device maps the two sequence elements one by one onto twosubcarriers in a same symbol based on the predefined mappingrelationship.

Assuming that the antenna port quantity is 4, the network devicedetermines that a CSI-RS corresponding to each antenna port may occupytwo REs in each RB (namely, an example of the resource unit) when CDM2is used, and may occupy four REs when CDM4 is used.

FIG. 6 and FIG. 7 are other schematic diagrams of pilot patternsaccording to an embodiment of the present invention. Specifically, FIG.6 and FIG. 7 show possible pilot patterns of CSI-RSs when an antennaport quantity is 4. As shown in FIG. 6, four REs used to carry a firstCSI-RS may be distributed in a same symbol. For example, four REs usedto carry the first CSI-RS shown in the figure are located in a symbol#5, and the four REs are located on a subcarrier #8 to a subcarrier #11.As shown in FIG. 7, the four REs used to carry the first CSI-RS may bedistributed in a same symbol, for example, the symbol #5 shown in thefigure, and the four REs are located on a subcarrier #4 to a subcarrier#7. By analogy, the four REs used to carry the first CSI-RS may belocated on a subcarrier #0 to a subcarrier #3 in a same symbol, which isnot shown in the figure. Moreover, the CSI-RSs at the four antenna portsmay be distinguished by using a multiplex code, in other words,frequency domain CDM is implemented.

When a quantity of REs used to carry the first CSI-RS in each resourceunit is greater than 2, at least two of the plurality of REs carrydifferent values of the first CSI-RS. Therefore, when the values areselected from a first pilot sequence for the first CSI-RS, two differentvalues of b (corresponding to the formula (2)), or two sets of differentvalues of (m, n) (corresponding to the formula (3)) may be selected. Inthe two sets of different values of (m, n) corresponding to the formula(3), for a determined resource unit, the value of m is given, and twodifferent values are selected for n. The specific process of selectingtwo different values from the first pilot sequence to generate the firstCSI-RS has been described in detail above with reference to the examplein which the antenna port quantity is 2. For brevity, details are notdescribed herein again.

It should be understood that, the correspondences between theabove-listed antenna port quantities and the pilot patterns and theschematic diagrams of the pilot patterns shown in the accompanyingdrawings are merely described as an example for ease of understanding,and should not be constructed as any limitation on this embodiment ofthe present invention. When the antenna port quantity is increased, forexample, the antenna port quantity is 8, twice CDM4 resources orfourfold CDM2 resources may also be considered to be used, to implementfrequency division multiplexing. Regardless of how the pilot pattern isconfigured, provided that at least two of the plurality of REs occupiedby the first CSI-RS in one symbol in one resource unit carry differentvalues of the CSI-RS, the configuration shall fall within the protectionscope of this embodiment of the present invention.

As described above, the network device may send a plurality of CSI-RSsby using a plurality of antenna ports, and the plurality of CSI-RSs maybe multiplexed on a time-frequency resource through frequency divisionCDM.

Optionally, in each resource unit, the plurality of REs used to carrythe first CSI-RS carry a second CSI-RS, at least two of the plurality ofREs used to carry the second CSI-RS carry different values of the secondCSI-RS, and the values of the second CSI-RS are loaded to the pluralityof REs by using a second multiplex code (for ease of distinguishing anddescription, a multiplex code corresponding to the second antenna portis denoted as the second multiplex code).

When the first CSI-RS and the second CSI-RS occupy a same RE, in a sameresource unit, a value of the first CSI-RS on an i^(th) (j>i≥0, i is aninteger, and j indicates a quantity of subcarriers in a resource unit)RE and a value of the second CSI-RS on the i^(th) RE are the same. Inthis case, the values may be distinguished by using different multiplexcodes.

Optionally, the multiplex code may be a CDM code, for example, an OCCcode.

The network device may distinguish between CSI-RSs at different antennaports through CDM. In other words, sequence elements configured on asame time-frequency resource (for example, an RE) are distinguished byusing the CDM code. Values of the CSI-RSs configured on a same RE may bethe same, but CDM codes corresponding to different antenna ports may bedifferent.

Using two antenna ports as an example, the OCC code may be two bits. Thenetwork device may distinguish between the two antenna ports by usingdifferent OCC codes. For example, corresponding to an antenna port(port) #15, a used OCC code may be [1, 1]; and corresponding to anantenna port (port) #16, a used OCC code may be [1, −1]. Therefore,although REs occupied by CSI-RSs at the port #15 and the port #16 arethe same and values of the CSI-RSs are the same, OCC codes aredifferent, and the two CSI-RSs may be orthogonal to each other byloading an orthogonal code, to avoid interference between each other.

S330. The network device sends the first CSI-RS to a terminal device byusing the plurality of REs.

When the network device sends the first CSI-RS to the terminal device byusing the plurality of REs, the resource unit is used as a minimum unitfor transmission, and in a same resource unit, other data different fromthe first CSI-RS may further be carried. Therefore, in S340, theterminal device receives signals sent by the network device, and thesignals include a first CSI-RS.

In addition, when two network devices send CSI-RSs by using a sametime-frequency resource and a same multiplex code, because a sequencelength of the CSI-RS in each resource unit is increased from 1 to atleast 2, correlation between sequences is reduced and interferencebetween the two CSI-RSs is reduced.

S340. The terminal device receives, on a plurality of resource units,signals sent by the network device, where the signals include a firstCSI-RS.

The terminal device may determine, with reference to the methodsdescribed in S310 and S320, the plurality of REs used to carry the firstCSI-RS from the network device.

Optionally, the method 300 further includes: receiving, by the terminaldevice, a configuration parameter sent by the network device, where theconfiguration parameter is used to determine the plurality of REscarrying the first CSI-RS.

Specifically, when sending the first CSI-RS to the terminal device, thenetwork device may send the configuration parameter to the terminaldevice, and the first parameter may include: for example, an antennaport quantity, a CSI-RS sending period, a system frame number, a numberof a symbol carrying the CSI-RS, a number of a resource unit (forexample, an RB) carrying the first CSI-RS, a CDM value, and a pilotdensity. The terminal device may determine, based on the firstparameter, the plurality of REs used to carry the first CSI-RS.

S350. The terminal device determines the plurality of resource elementsREs used to carry the first CSI-RS, and obtain the first CSI-RS from theplurality of REs.

The terminal device determines, in S350, the plurality of REs carryingthe first CSI-RS, so that the terminal device can obtain the firstCSI-RS from the signals received in S340.

It may be understood by a person skilled in the art that, the firstCSI-RS sent by the network device may be x, and the network device sendsthe first CSI-RS to the terminal device through a channel by using theplurality of REs. Therefore, the signals received by the terminal devicemay be y. A relationship between the vector x of the first CSI-RS sentby the network device and the vector y of signal received by theterminal device may be represented as follows:

y=Hx+n

where H represents a channel matrix, and n represents receiver noise. Itmay be learned that the receiver noise n causes impact on signalreceiving. In this embodiment of the present invention, for ease ofdescription, it is assumed that the receiver noise is zero and a signalis correctly transmitted. In the prior art, there are a plurality ofsolutions that can be used to eliminate the noise. For brevity, adescription of same or similar cases is omitted below.

Optionally, the method 300 further includes: generating, by the terminaldevice, a third CSI-RS.

In this embodiment of the present invention, for ease of distinguishingand description, the CSI-RS generated by the terminal device is denotedas the third CSI-RS.

It should be understood that, the terminal device may first generate asecond pilot sequence based on the first parameter, and then determine avalue of the third CSI-RS based on the above-described mappingrelationship between a sequence element and an RE in the pilot pattern,and the plurality of REs for the first CSI-RS determined in S340, toobtain the third CSI-RS. It should be understood that, a specificprocess of generating the third CSI-RS by the terminal device is similarto the specific processes of generating the first pilot sequence by thenetwork device based on the first parameter and determining theplurality of REs used to carry the first CSI-RS in S310 and S320. Forbrevity, details are not described herein again.

Moreover, because first parameters used by the network device and theterminal device are the same, formulas used to generate the pilotsequence are the same, and mapping relationships between a sequenceelement and an RE are the same, the third CSI-RS generated by theterminal device is the same as the first CSI-RS generated by the networkdevice, in other words, the third CSI-RS may be represented as thevector x.

Optionally, the method 300 further includes: estimating, by the terminaldevice, a channel matrix based on the received first CSI-RS and thegenerated third CSI-RS.

It can be learned from the description of S350 that the first CSI-RSreceived by the terminal device may bey, and the third CSI-RS generatedby the terminal device based on the first parameter may be x. Therefore,an estimated value of H may be solved according to y=Hx+n.

The terminal device can estimate the channel matrix by using theforegoing steps, to determine a precoding matrix for data transmission.

Therefore, in this embodiment of the present invention, in a pluralityof REs used to carry CSI-RSs at antenna ports, at least two REs in eachresource unit have different CSI-RS values, in other words, a sequencelength of a CSI-RS at each antenna port in each symbol in each resourceunit is increased, correlation between pilot sequences is reduced, andinterference between the CSI-RSs is reduced, thereby facilitating moreaccurate channel estimation.

It should be understood that, details of the reference signal sendingmethod and the reference signal receiving method according to theembodiments of the present invention are described in the foregoingembodiments by using a PN sequence as an example. However, this shouldnot be constructed as any limitation on this embodiment of the presentinvention. This application does not exclude a possibility of generatinga pilot sequence by using another sequence, for example, a ZC sequence,in a future protocol either. The reference signal sending method and thereference signal receiving method according to the embodiments of thepresent invention are also applicable to other sequences, to increase asequence length and reduce correlation between pilot sequences. Forbrevity, other sequences are not described one by one herein as anexample.

It should be understood that sequence numbers of the processes do notmean execution sequences in the foregoing embodiments. The executionsequences of the processes should be determined according to functionsand internal logic of the processes, and should not be constructed asany limitation on the implementation processes of embodiments of thisapplication.

The foregoing describes the reference signal sending method and thereference signal receiving method in the embodiments of the presentinvention in detail with reference to FIG. 3 to FIG. 7. The followingdescribes the network device and the terminal device in the embodimentsof the present invention in detail with reference to FIG. 8 to FIG. 11.

FIG. 8 is a schematic block diagram of a network device 10 according toan embodiment of the present invention. As shown in FIG. 8, the networkdevice 10 includes a determining module 11 and a transceiver module 12.

The determining module 11 is configured to determine a plurality ofresource elements REs used to carry a first CSI-RS, where the pluralityof REs are distributed in a plurality of resource units. In eachresource unit, a plurality of REs used to carry the first CSI-RS arelocated on a plurality of subcarriers in a same symbol, values of thefirst CSI-RS carried on at least two REs are different, and values ofthe first CSI-RS are loaded to the plurality of REs in the resource unitby using a first multiplex code.

The transceiver 12 is configured to send the first CSI-RS to a terminaldevice by using the plurality of REs.

Optionally, in each resource unit, a quantity of the plurality ofsubcarriers in the same symbol is at least one of {2,4,8,12}.

Optionally, the values of the first CSI-RS carried on the plurality ofREs in each resource unit are different from each other.

Optionally, the plurality of REs carry a second CSI-RS, values of thesecond CSI-RS carried on at least two REs are different, and values ofthe second CSI-RS are loaded to the plurality of REs by using a secondmultiplex code.

Optionally, the values of the first CSI-RS are calculated by using thefollowing formula:

r _(l,n) _(s) (b)=g(b), b=0, 1, . . . , N−1

where N=f(a, N_(RB) ^(max,DL)), a is a first parameter N_(RB) ^(max,DL)represents a maximum quantity of resource units included on a downlinkchannel, and r_(l,n) _(s) (b) represents a value of a b^(th) CSI-RS inan l^(th) symbol in an n_(s) ^(th) slot.

Optionally, the values of the first CSI-RS are calculated by using thefollowing formula:

r _(l,n) _(s) (m, n)=h(m, n), m=0, 1, . . . , N _(RB) ^(max,DL)−1, n=0,1, . . . , a−1

where a is a first parameter, N_(RB) ^(max,DL) represents a maximumquantity of resource units included on a downlink channel, and r_(l,n)_(s) (m, n) represents a value of an n^(th) CSI-RS in an m^(th) resourceunit in an l^(th) symbol in an n_(s) ^(th) slot.

Optionally, a value of the first parameter a includes at least one ofthe following: a quantity of REs in one symbol in one resource unit; alength of an orthogonal code used by a CSI-RS port during frequencydomain code division multiplexing; or a quantity of REs occupied by aCSI-RS port in one symbol in one resource unit.

Optionally, the value of the first parameter a includes at least one of{2,4,8,12}.

Optionally, the first parameter a is preconfigured.

Optionally, the first parameter a is sent to the terminal device afterbeing determined by the network device.

It should be understood that, the network device 10 may correspond tothe network device in the reference signal sending or reference signalreceiving method 300 according to embodiments of the present invention,and the network device 10 may include modules configured to perform themethod performed by the network device in the reference signal sendingor reference signal receiving method 300 in FIG. 3. Moreover, thevarious modules in the network device 10 and other operations and/orfunctions described above are for the purpose of implementing acorresponding procedure of the reference signal sending or referencesignal receiving method 300 in FIG. 3. Specifically, the determiningmodule 11 may be configured to perform S310 and S320 in the method 300,and the transceiver module 12 may be configured to perform S330 in themethod 300. Exemplary processes of performing the foregoingcorresponding steps by the various modules have been described in detailin the method 300, and for brevity, details are not described hereinagain.

FIG. 9 is a schematic block diagram of a terminal device 20 according toan embodiment of the present invention. As shown in FIG. 9, the terminaldevice 20 includes a transceiver module 21, a determining module 22, andan obtaining module 23.

The transceiver module 21 is configured to receive, on a plurality ofresource units, signals sent by a network device, where the signalsinclude a first CSI-RS.

The determining module 22 is configured to determine a plurality ofresource elements REs used to carry the first CSI-RS, where theplurality of REs are distributed in a plurality of resource units, andin each resource unit, a plurality of REs used to carry the first CSI-RSare located on a plurality of subcarriers in a same symbol, values ofthe first CSI-RS carried on at least two REs are different, and valuesof the first CSI-RS are loaded to the plurality of REs in the resourceunit by using a first multiplex code.

The obtaining module 23 is configured to obtain the first CSI-RS on theplurality of REs.

Optionally, in each resource unit, a quantity of the plurality ofsubcarriers in the same symbol is at least one of {2,4,8,12}.

Optionally, the values of the first CSI-RS carried on the plurality ofREs are different from each other. Optionally, the values of the firstCSI-RS are calculated by using the following formula:

r _(l,n) _(s) (b)=g(b), b=0, 1, . . . , N−1

where N=f(a, N_(RB) ^(max,DL)), a is a first parameter N_(RB) ^(max,DL)represents a maximum quantity of resource units included on a downlinkchannel, and r_(l,n) _(s) (b) represents a value of a b^(th) CSI-RS inan l^(th) symbol in an n_(s) ^(th) slot.

Optionally, the values of the first CSI-RS are calculated by using thefollowing formula:

r _(l,n) _(s) (m, n)=h(m, n), m=0, 1, . . . , N _(RB) ^(max,DL)−1, n=0,1, . . . , a−1

where a is a first parameter, N_(RB) ^(max,DL) represents a maximumquantity of resource units included on a downlink channel, and r_(l,n)_(s) (m, n) represents a value of an n^(th) CSI-RS in an m^(th) resourceunit in an l^(th) symbol in an n_(s) ^(th) slot.

Optionally, a value of the first parameter a includes at least one ofthe following: a quantity of REs in one symbol in one resource unit; alength of an orthogonal code used by a CSI-RS port during frequencydomain code division multiplexing; or a quantity of REs occupied by aCSI-RS port in one symbol in one resource unit.

Optionally, the first parameter a is predetermined by the network deviceor the terminal device.

Optionally, the first parameter a is sent to the terminal device afterbeing determined by the network device.

It should be understood that, the terminal device 20 may correspond tothe terminal device in the reference signal sending or reference signalreceiving method 300 according to the embodiments of the presentinvention, and the terminal device 20 may include modules configured toperform the method performed by the terminal device in the referencesignal sending or reference signal receiving method 300 in FIG. 3.Moreover, the various modules in the terminal device 20 and otheroperations and/or functions described above are for the purpose ofimplementing a corresponding procedure of the reference signal sendingor reference signal receiving method 300 in FIG. 3. Specifically, thetransceiver module 21 may be configured to perform S340 in the method300, and the determining module 22 and the obtaining module 23 may beconfigured to perform S350 in the method 300. Exemplary processes ofperforming the foregoing corresponding steps by the various modules havebeen described in detail in the method 300, and for brevity, details arenot described herein again.

FIG. 10 is another schematic block diagram of a network device 400according to an embodiment of the present invention. As shown in FIG.10, the network device 400 includes a processor 410 and a transceiver420, and optionally, the network device 400 further includes a memory430. The processor 410, the transceiver 420, and the memory 430communicate with each other by using an internally connected channel totransmit a control and/or data signal, the memory 430 is configured tostore a computer program, and the processor 410 is configured to invokethe computer program from the memory 430 and run the computer program,to control the transceiver 420 to receive or send a signal. When thecomputer program stored in the memory 430 is executed by the processor410, the processor 410 is configured to determine a plurality ofresource elements REs used to carry a first CSI-RS, where the pluralityof REs are distributed in a plurality of resource units, and in eachresource unit, a plurality of REs used to carry the first CSI-RS arelocated on a plurality of subcarriers in a same symbol, values of thefirst CSI-RS carried on at least two REs are different, and values ofthe first CSI-RS are loaded to the plurality of REs in the resource unitby using a first multiplex code; and the transceiver 420 is configuredto send the first CSI-RS to a terminal device by using the plurality ofREs.

The processor 410 and the memory 430 may be combined into one processingapparatus, and the processor 410 is configured to execute the computerprogram stored in the memory 430 to implement the foregoing functions.In an exemplary implementation, the memory 430 may be integrated intothe processor 410, or independent of the processor 410.

The network device may further include an antenna 440, configured tosend, by using a radio signal, downlink data or downlink controlsignaling output by the transceiver 420. Specifically, the networkdevice 400 may correspond to the network device in the reference signalsending or reference signal receiving method 300 according toembodiments of the present invention, and the network device 400 mayinclude units configured to perform operations performed by the networkdevice in the reference signal sending or reference signal receivingmethod 300 in FIG. 3. Moreover, the various units in the network device30 and other operations and/or functions described above are for thepurpose of implementing a corresponding procedure of the referencesignal sending or reference signal receiving method 300 in FIG. 3.Specifically, the memory 430 is configured to store program code, sothat when the processor 410 executes the program code, the processor 410performs S310 and S320 in the method 300, and controls the transceiver420 to perform S330 in the method 300 by using the antenna 440.Exemplary processes of performing the foregoing corresponding steps bythe various units have been described in detail in the method 300, andfor brevity, details are not described herein again.

FIG. 11 is another schematic block diagram of a terminal device 500according to an embodiment of the present invention. As shown in FIG.11, the terminal device 500 includes a processor 501 and a transceiver502, and optionally, the terminal device 500 further includes a memory503. The processor 501, the transceiver 502, and the memory 503communicate with each other by using an internally connected channel totransmit a control and/or data signal, the memory 503 is configured tostore a computer program, and the processor 501 is configured to invokethe computer program from the memory 503 and run the computer program,to control the transceiver 502 to receive or send a signal.

When the computer program stored in the memory 503 is executed by theprocessor 501, the processor 501 is configured to determine a pluralityof resource elements REs used to carry a first CSI-RS from a networkdevice, where the plurality of REs are distributed in a plurality ofresource units, and in each resource unit, a plurality of REs used tocarry the first CSI-RS are located on a plurality of subcarriers in asame symbol, values of the first CSI-RS carried on at least two REs aredifferent, and values of the first CSI-RS are loaded to the plurality ofREs in the resource unit by using a first multiplex code; and thetransceiver 502 is configured to receive signals sent by the networkdevice, where the signals include a first CSI-RS, and the processor 501is further configured to obtain the first CSI-RS on the plurality ofREs.

The processor 501 and the memory 503 may be combined into one processingapparatus, and the processor 501 is configured to execute the computerprogram stored in the memory 503 to implement the foregoing functions.In an exemplary implementation, the memory 503 may be integrated intothe processor 501, or independent of the processor 501. The terminaldevice 500 may further include an antenna 504, configured to send, byusing a radio signal, uplink data or uplink control signaling output bythe transceiver 502.

Specifically, the terminal device 500 may correspond to the terminaldevice in the reference signal sending or reference signal receivingmethod 300 according to embodiments of the present invention, and theterminal device 500 may include modules configured to perform operationsperformed by the terminal device in the reference signal sending orreference signal receiving method 300 in FIG. 3. Moreover, the variousmodules in the terminal device 500 and other operations and/or functionsdescribed above are for the purpose of implementing a correspondingprocedure of the reference signal sending or reference signal receivingmethod 300 in FIG. 3. Specifically, the memory 503 is configured tostore program code, so that when the processor 501 executes the programcode, the processor 501 controls the transceiver 502 to perform S340 inthe method 300 and perform S350 in the method 300 by using the antenna504. Exemplary processes of performing the foregoing corresponding stepsby the various modules have been described in detail in the method 300,and for brevity, details are not described herein again.

The processor 501 may be configured to perform an action implementedinside a terminal as described in the foregoing method embodiments, andthe transceiver 502 may be configured to perform an action oftransmission or sending from a terminal to a network device as describedin the foregoing method embodiments. For details, refer to thedescriptions of the foregoing method embodiments, and details are notdescribed herein again.

The processor 501 and the memory 503 may be integrated into oneprocessing apparatus, and the processor 501 is configured to execute thecomputer program stored in the memory 503 to implement the foregoingfunctions. In an exemplary implementation, the memory 503 mayalternatively be integrated into the processor 501.

The foregoing terminal device 500 may further include a power supply505, configured to supply power to various components or circuits in theterminal.

In addition, to perform functions of the terminal device, the terminaldevice 500 may further include one or more of an input unit 506, adisplay unit 507, an audio circuit 508, a camera 509, and a sensor 510,and the audio circuit may further include a speaker 5082, a microphone5084, and the like.

It should be understood that, the processor in this embodiment of thepresent invention may be a central processing unit (CPU), or may furtherbe another general purpose processor, a digital signal processor (DSP),an application-specific integrated circuit (ASIC), a field programmablegate array (FPGA), or another programmable logic device, discrete gateor transistor logic device, discrete hardware component, or the like.

It should be further understood that the memory in this embodiment ofthe present invention may be a volatile memory or a nonvolatile memory,or may include a volatile memory and a nonvolatile memory. Thenonvolatile memory may be a read-only memory (ROM), a programmableread-only memory (programmable ROM, PROM), an erasable programmableread-only memory (erasable PROM, EPROM), an electrically erasableprogrammable read-only memory (electrically EPROM, EEPROM), or a flashmemory. The volatile memory may be a random access memory (RAM), used asan external cache. Through example but not limitative description, manyforms of random access memories (RAM) may be used, for example, a staticrandom access memory (static RAM, SRAM), a dynamic random access memory(DRAM), a synchronous dynamic random access memory (synchronous DRAM,SDRAM), a double data rate synchronous dynamic random access memory(double data rate SDRAM, DDR SDRAM), an enhanced synchronous dynamicrandom access memory (enhanced SDRAM, ESDRAM), a synchronous linkdynamic random access memory (synchlink DRAM, SLDRAM), and a directrambus random access memory (direct rambus RAM, DR RAM).

All or some of the foregoing embodiments may be implemented throughsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, the foregoing embodiments may beimplemented partially in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instructions are loaded or executed on acomputer, the procedure or functions according to the embodiments of thepresent invention are all or partially generated. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, orother programmable apparatuses. The computer instructions may be storedin a computer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (for example, infrared, radio, andmicrowave, or the like) manner. The computer-readable storage medium maybe any usable medium accessible by a computer, or a data storage device,such as a server or a data center, integrating one or more usable media.The usable medium may be a magnetic medium (for example, a floppy disk,a hard disk, and a magnetic tape), an optical medium (for example, adigital versatile disc (DVD)), or a semiconductor medium. Thesemiconductor medium may be a solid-state drive.

The term “and/or” in this specification describes only an associationrelationship for describing associated objects and represents that threerelationships may exist. For example, A and/or B may represent thefollowing three cases: Only A exists, both A and B exist, and only Bexists. In addition, the character “/” in this specification generallyindicates an “or” relationship between the associated objects.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of this application.

It may be clearly understood by a person skilled in the art that, forthe purpose of convenient and brief description, for a detailed workingprocess of the foregoing system, apparatus, and unit, refer to acorresponding process in the foregoing method embodiments, and detailsare not described herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualrequirements to achieve objectives of solutions of embodiments.

In addition, functional units in embodiments of this application may beintegrated into one processing unit, or each of the units may existalone physically, or two or more units are integrated into one unit.

When the functions are implemented in the form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer-readable storage medium. Based on such anunderstanding, technical solutions of this application may beimplemented in a form of a software product. The software product isstored in a storage medium, and includes several instructions forinstructing a computer device (which may be a personal computer, aserver, a network device, or the like) to perform all or some of thesteps of the methods described in the embodiments of this application.The foregoing storage medium includes: any medium that can store programcode, such as a Universal Serial Bus (USB) flash drive, a removable harddisk, a read-only memory (ROM), a random access memory (RAM), a magneticdisk, or a compact disc.

The foregoing descriptions are merely exemplary implementations of thisapplication, and are not intended to limit the protection scope of thisapplication. Any variation or replacement readily figured out by aperson skilled in the art within the technical scope disclosed in thisapplication may fall within the protection scope of this application.The protection scope of this application shall be subject to theprotection scope of the claims.

Additionally, statements made herein characterizing the invention referto an embodiment of the invention and not necessarily all embodiments.

1. A reference signal receiving method, comprising: receiving, by aterminal device on a plurality of resource units, signals sent by anetwork device, wherein the signals comprise a first channel stateinformation reference signal (CSI-RS); determining, by the terminaldevice, a plurality of resource elements (REs) used to carry the firstCSI-RS, wherein the plurality of REs are distributed in a plurality ofresource units, and wherein in each resource unit, multiple REs of theplurality of REs are located on a plurality of subcarriers in a samesymbol, values of the first CSI-RS carried on at least two REs aredifferent, and values of the first CSI-RS are loaded to the multiple REsin the resource unit by using a first multiplex code; and obtaining, bythe terminal device, the first CSI-RS on the determined plurality ofREs.
 2. The method according to claim 1, wherein values of the firstCSI-RS carried on all REs in each resource unit are different from eachother.
 3. The method according to claim 1, wherein the multiple REs ineach resource unit carry a second CSI-RS, values of the second CSI-RScarried on at least two REs are different, and values of the secondCSI-RS are loaded to the multiple REs in each resource unit by using asecond multiplex code.
 4. The method according to claim 1, wherein thevalues of the first CSI-RS are from a first pilot sequence, the firstpilot sequence is correlated to a first parameter a, and a value of thefirst parameter a comprises at least one of the following: a length ofan orthogonal code used by a CSI-RS port during frequency domain codedivision multiplexing; or a quantity of REs occupied by a CSI-RS port inone symbol in one resource unit.
 5. The method according to claim 4,wherein the terminal device receives, by using Radio Resource Control(RRC) signaling, the first parameter a from the network device.
 6. Themethod according to claim 1, wherein the values of the first CSI-RS arefrom a first pilot sequence, the first pilot sequence is correlated tothe first parameter a, and the value of the first parameter a comprises2.
 7. A terminal device, comprising: a transceiver configured toreceive, on a plurality of resource units, signals sent by a networkdevice, wherein the signals comprise a first channel state informationreference signal (CSI-RS); and at least one of processor configured todetermine a plurality of resource elements (REs) used to carry the firstCSI-RS, wherein the plurality of REs are distributed in a plurality ofresource units, and wherein in each resource unit, multiple REs of theplurality of REs are located on a plurality of subcarriers in a samesymbol, values of the first CSI-RS carried on at least two REs aredifferent, and values of the first CSI-RS are loaded to the multiple REsin the resource unit by using a first multiplex code; wherein the atleast one of processor is further configured to obtain the first CSI-RSon the determined plurality of REs.
 8. The terminal device according toclaim 7, wherein values of the first CSI-RS carried on all REs in eachresource unit are different from each other.
 9. The terminal deviceaccording to claim 7, wherein the multiple REs in each resource unitfurther carry a second CSI-RS, values of the second CSI-RS carried on atleast two REs are different, and values of the second CSI-RS are loadedto the multiple REs in each resource unit by using a second multiplexcode.
 10. The terminal device according to claim 7, wherein the valuesof the first CSI-RS are from a first pilot sequence, the first pilotsequence is correlated to a first parameter a, and a value of the firstparameter a comprises at least one of the following: a length of anorthogonal code used by a CSI-RS port during frequency domain codedivision multiplexing; or a quantity of REs occupied by a CSI-RS port inone symbol in one resource unit.
 11. The terminal device according toclaim 7, wherein the values of the first CSI-RS are from a first pilotsequence, the first pilot sequence is correlated to the first parametera, and the value of the first parameter a comprises
 2. 12. The terminaldevice according to claim 11, wherein the transceiver is furtherconfigured to receive, by using Radio Resource Control (RRC) signaling,the first parameter a from the network device.
 13. A non-transitorycomputer-readable medium having processor-executable instructions storedthereon for performing a reference signal receiving method, wherein theprocessor-executable instructions, when executed, facilitate: receivingsignals comprising a first channel state information reference signal(CSI-RS); determining a plurality of resource elements (REs) used tocarry the first CSI-RS, wherein the plurality of REs are distributed ina plurality of resource units, and wherein in each resource unit,multiple REs of the plurality of REs are located on a plurality ofsubcarriers in a same symbol, values of the first CSI-RS carried on atleast two REs are different, and values of the first CSI-RS are loadedto the multiple REs in the resource unit by using a first multiplexcode; and obtaining the first CSI-RS on the determined plurality of REs.14. The non-transitory computer readable medium according to claim 13,wherein values of the first CSI-RS carried on all REs in each resourceunit are different from each other.
 15. The non-transitory computerreadable medium according to claim 13, wherein the multiple REs in eachresource unit carry a second CSI-RS, values of the second CSI-RS carriedon at least two REs are different, and values of the second CSI-RS areloaded to the multiple REs in each resource unit by using a secondmultiplex code.
 16. The non-transitory computer readable mediumaccording to claim 13, wherein the values of the first CSI-RS are from afirst pilot sequence, the first pilot sequence is correlated to a firstparameter a, and a value of the first parameter a comprises at least oneof the following: a length of an orthogonal code used by a CSI-RS portduring frequency domain code division multiplexing; or a quantity of REsoccupied by a CSI-RS port in one symbol in one resource unit.
 17. Thenon-transitory computer readable medium according to claim 16, whereinthe value of the first parameter a comprises
 2. 18. A processingapparatus, comprising: a memory having program code stored thereon; andat least one processor configured to execute the program code stored inthe memory to facilitate performance of a reference signal receivingmethod, wherein the reference signal receiving method comprises:receiving signals comprising a first channel state information referencesignal (CSI-RS); determining a plurality of resource elements (REs) usedto carry the first CSI-RS, wherein the plurality of REs are distributedin a plurality of resource units, and wherein in each resource unit,multiple REs of the plurality of REs are located on a plurality ofsubcarriers in a same symbol, values of the first CSI-RS carried on atleast two REs are different, and values of the first CSI-RS are loadedto the multiple REs in the resource unit by using a first multiplexcode; and obtaining the first CSI-RS on the determined plurality of REs.19. The processing apparatus according to claim 18, wherein the memoryis integrated in or independent of the at least one processor.
 20. Theprocessing apparatus according to claim 18, wherein values of the firstCSI-RS carried on all REs in each resource unit are different from eachother.
 21. The processing apparatus according to claim 18, wherein themultiple REs in each resource unit carry a second CSI-RS, values of thesecond CSI-RS carried on at least two REs are different, and values ofthe second CSI-RS are loaded to the multiple REs in each resource unitby using a second multiplex code.
 22. The processing apparatus accordingto claim 18, wherein the values of the first CSI-RS are from a firstpilot sequence, the first pilot sequence is correlated to a firstparameter a, and a value of the first parameter a comprises at least oneof the following: a length of an orthogonal code used by a CSI-RS portduring frequency domain code division multiplexing; or a quantity of REsoccupied by a CSI-RS port in one symbol in one resource unit.
 23. Theprocessing apparatus according to claim 22, wherein the value of thefirst parameter a comprises 2.